The present invention relates to the field of solid phase chemistry. More specifically, the invention provides a method for solid phase and combinatorial synthesis of organic compounds, and most particularly, a therapeutically important class of compounds, namely diversely substituted 3-aminothiophenes.
Obtaining a better understanding of the important factors in molecular recognition in conjunction with developing new therapeutic agents is a major focus of scientific research. Methods have recently been developed, which permit the fast generation of large arrays of pure compounds or of mixtures of compounds, which are then screened against a specific receptor or enzyme. However, there are still only few methods available for the fast synthesis of organic compounds other than peptides or oligonucleotides. The latter tend to have very short clearing times, so that their utility as bioavailable therapeutic agent will be limited. For this reason, organic compounds of potential therapeutic interest are today still synthesized and evaluated one at a time, thus dramatically limiting the number of derivatives which can be screened. It is therefore of utmost importance to develop new synthetic methodology, which permits the fast synthesis of bioavailable organic compounds of potential therapeutic interest, such as small heterocyclic compounds. This could be achieved by developing a solid phase synthesis for such compounds, since experience has shown, that solid phase synthesis is amenable to automatization and can yield products of high purity without the need of any tedious and time consuming purification steps.
The realization of known synthetic reactions on a solid support may not always be possible and may require careful optimization of the reaction conditions. Although solid phase synthesis, once implemented and optimized, offers many advantages if compared to syntheses in liquid phase, the finding of the appropriate reaction conditions may be a difficult task. This may be due to the limited choice of solvents which may be used with some types of supports, as well as the difficulty of precise temperature adjustment in arrays of reactors for solid phase synthesis. Additionally, the classical tools for the quality control of intermediates (infrared spectroscopy, nuclear magnetic resonance spectroscopy, mass spectrometry) may only be of limited use in solid phase synthesis. For these reasons, the implementation of known reactions to a solid support may often require a major effort and time investment.
The synthetic sequence disclosed in this invention is a variant of related thiophene syntheses (ref. 11-16), adapted and optimized for its realization on a solid support.
Terminology
The following terms are intended to have the following, general meanings:
1. Substrate: refers to any insoluble or partially insoluble material, to which compounds may be covalently attached. Substrates may be selected from the group consisting of any kind of organic or inorganic polymeric or oligomeric compound, e.g. polystyrene with different grades of crosslinking, polyethylene glycol (PEG), polyethylene glycol attached to polystyrene (e.g. TentaGel), polyacrylamides, polyacrylates, polyurethanes, polycarbonates, polyamides, polysaccharides or silicates. PA1 2. Linker: a molecule with at least two reactive sites, which permit its covalent attachment to other molecules or to a substrate. Either the bond of the linker to the substrate or the bond of the linker to other molecules attached to it or the linker itself must be cleavable upon selective exposure to an activator such as a selected chemical activator or other specific conditions, e.g. by treatment with a strong acid or by exposure to electromagnetic radiation or by metal catalysis. PA1 3. Array: A collection of N single compounds or N mixtures of compounds with a common structural element, synthesized simultaneously in a parallel fashion using the same synthetic reaction sequence. The precise structure of a single compound within an array of compounds or the components of a mixture within an array of mixtures is determined by the sequence of reactants which gave rise to this compound or mixture and can be deduced from the recorded reaction-protocol. The spatial arrangement of the array is irrelevant. PA1 4. Thiophene: Five-membered heteroaromatic compound containing one sulphur atom in the five-membered ring. PA1 5. Protecting group: A material which is chemically bound to a molecule or a substrate and which may be removed upon selective exposure to an activator such as a selected chemical activator or other specific conditions, e.g. by treatment with a strong acid or by exposure to electromagnetic radiation or by metal catalysis. PA1 6. Combinatorial synthesis: an ordered strategy for parallel synthesis of arrays of single compounds or mixtures, by sequential addition of reagents. PA1 7. Receptor: A material that has an affinity for a given ligand. Receptors may be naturally-occurring or synthetic molecules or aggregates of molecules. Also, they can be employed in their unaltered state or as aggregates with other species. Receptors may be attached, covalently or non-covalently, to a binding material or a substrate, either directly or via a linking substance. Examples of receptors which can be employed by this invention include, but are not restricted to, antibodies, monoclonal antibodies and antisera reactive with specific antigenic determinants (such as viruses, cells or other materials), cell membrane receptors, drugs, oligonucleotides, polynucleotides, nucleic acids, peptides, cofactors, small organic molecules, lectins, sugars, oligosaccharides, cells, cellular membranes, organelles, microorganism receptors, enzymes, catalytic polypeptides, hormone receptors, primary metabolite receptors such as carbohydrate receptors, nucleotide receptors or lipid receptors and secondary metabolite receptors such as opiate receptors, prostaglandine receptors, etc. PA1 8. Abbreviations: The following frequently used abbreviations are intended to have the following meanings: PA1 R.sup.6 is hydrogen, alkyl optionally substituted with hydroxy, halogen, cyano, alkoxy, aryloxy, dialkylamino, arylalkylamino or diarylamino; or aralkyl; PA1 R.sup.5 and R.sup.6 may be covalently linked to each other by a covalent bond or an additional alkylene group R.sup.5, preferentially giving rise to a fragment of the type shown below ##STR3## wherein n and m are integers between 0 and 15, preferentially 0 and 3; R.sup.7 is hydrogen, alkyl, alkyl substituted with hydroxy, alkoxy, aryloxy, alkylthio, arylthio, dialkylamino, arylalkylamino or diarylamino; aralkyl, aryl, aryl substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl; PA1 R.sup.1 is hydrogen, alkyl optionally substituted with hydroxy, halogen, cyano, alkoxy, aryloxy, dialkylamino, arylalkylamino or diarylamino; or aralkyl; PA1 R.sup.1 may be covalently linked to A, R.sup.5, R.sup.6 and/or R.sup.7, in which case --R.sup.1 --A-- or --R.sup.1 --R.sup.5 -- represents low alkylene, preferentially methylene, ethylene or propylene, unsubstituted or substituted with alkyl, hydroxy, alkoxycarbonyl, alkoxy or dialkylamino, --R.sup.1 --R.sup.6 -- represents ethylene or propylene, unsubstituted or substituted with alkyl, hydroxy, alkoxy or dialkylamino, and/or --R.sup.1 --R.sup.7 -- represents methylene, propylene or butylene unsubstituted or substituted with alkyl, hydroxy, alkoxycarbonyl, alkoxy or dialkylamino; PA1 R.sup.2 is alkyl optionally substituted with aryl, heteroaryl, alkoxy, aryloxy, cyano, dialkylamino, arylalkylamino, diarylamino or halogen; aryl optionally substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl; heteroaryl optionally substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl; and PA1 R.sup.3 is cyano, nitro, --CO--R' or --C(OH)--R', R' being alkyl, alkyl substituted with halogen, aryl, aryl substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl or heteroaryl; or --SO.sub.2 R", R" being alkyl or substituted or unsubstituted aryl. PA1 R.sup.4 is hydrogen or COZ, Z being substituted or unsubstituted alkyl, aryl, arylamino or alkylamino; and PA1 pharmaceutically acceptable salts thereof; PA1 A' is a chemical bond or a group of formula ##STR5## wherein R.sup.5 is alkylene optionally substituted with hydrogen, alkyl, aryl, heteroaryl, alkoxy, aryloxy, cyano, hydroxy, dialkylamino, arylalkylamino, diarylamino or halogen; PA1 R.sup.6 is hydrogen, alkyl optionally substituted with hydroxy, halogen, cyano, alkoxy, aryloxy, dialkylamino, arylalkylamino or diarylamino; or aralkyl; PA1 R.sup.5 and R.sup.6 may be covalently linked to each other by a covalent bond or an additional alkylene group R.sup.5, preferentially giving rise to a fragment of the type shown below ##STR6## wherein n and m are integers between 0 and 15, preferentially 0 and 3; PA1 R.sup.1 is hydrogen, alkyl optionally substituted with hydroxy, halogen, cyano, alkoxy, aryloxy, dialkylamino, arylalkylamino or diarylamino; or aralkyl; PA1 R.sup.1 may be covalently linked to A, R.sup.5, R.sup.6 and/or R.sup.7, in which case --R.sup.1 --A-- or --R.sup.1 --R.sup.5 -- represents low alkylene, preferentially methylene, ethylene or propylene, unsubstituted or substituted with alkyl, hydroxy, alkoxycarbonyl, alkoxy or dialkylamino, --R.sup.1 --R.sup.6 -- represents ethylene or propylene, unsubstituted or substituted with alkyl, hydroxy, alkoxy or dialkylamino, and/or --R.sup.1 --R.sup.7 -- represents methylene, propylene or butylene unsubstituted or substituted with alkyl, hydroxy, alkoxycarbonyl, alkoxy or dialkylamino; PA1 R.sup.2 is alkyl optionally substituted with aryl, heteroaryl, alkoxy, aryloxy, cyano, hydroxy, dialkylamino, arylalkylamino, diarylamino or halogen; aryl optionally substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl; heteroaryl optionally substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl; and PA1 R.sup.3 is cyano, nitro, --CO--R' or --C(OH)--R', R' being alkyl, alkyl substituted with halogen, aryl, aryl substituted with alkyl, aryl, heteroaryl, halogen, alkoxy, aryloxy, dialkylamino, alkylarylamino, diarylamino, halogen, cyano, alkoxycarbonyl or aminocarbonyl or heteroaryl; or --SO.sub.2 R", R" being alkyl or substituted or unsubstituted aryl. PA1 R.sup.4 is hydrogen or COZ, Z being substituted or unsubstituted alkyl, aryl, arylamino or alkylamino; PA1 and pharmaceutically acceptable salts thereof.
AcOH: glacial acetic acid PA2 DBU: 1,8-diazabicyclo[5.4.0]undec-7-ene PA2 DCM: dichloromethane, methylenechloride PA2 DMF: N,N-dimethyl formamide PA2 FMoc: fluorenylmethyloxycarbonyl PA2 R: organic radical PA2 TFA: trifluoroacetic acid PA2 THF: tetrahydrofurane